The following sound examples are some types of 'background noise' that can be added to other sounds to simulate real-world conditions. It seems a little hopeless to try and enumerate all the possible kinds of noise that might be encountered - in general, noise refers to anything unwanted, which could be, well, anything. However, noise robustness is such an important consideration that various efforts have been made to assemble collections of 'typical' noise backgrounds.
The examples below are based on the ones constructed for the AURORA noisy speech evaluation. Each example is 10 seconds long, and is sampled at 8 kHz.
The following examples were recorded with a pair of binaural mics (Soundman OKMIIKs, worn in my ears) and directly encoded to joint-stereo MP3s with my Neuros audio processor.